Refining of effluent from in situ combustion operation



April 30, 1968 M. 1 HENDERsoN REFINING OF' EFFLUENT FROM IN SITUCOMBUS'IION OPERATION Filed Dec. 28, 1964 VA E393@ A TTORNEVS UnitedStates Patent O 3,380,913 REFINING OF EFFLUENT FROM IN SI'IU `COMBUSTIONOPERATION Miles L. Henderson, Bartlesville, Okla., assignor to PhillipsPetroleum Company, a corporation of Delaware Filed Dec. 28, 1964, Ser.No. 421,189 2 Claims. (Cl. 208-187) ABSTRACT OF THE DISCLOSURE A hot,high pressure vapor-liquid mixture from an in situ combustion operationis charged to a sand trap and vapor-liquid separator to remove sand andrecover a vapor stream of N2, H2O, and hydrocarbons boiling in the gasoil range and lower at relatively high pressure and temperature and aliquid stream of water and higher boiling hydrocarbons. The latterstream is flashed to separate an overhead vapor stream and a bottomsliquid stream of high boiling hydrocarbons and water in the form of anemulsion. This emulsion is broken into an overhead vapor stream, abottoms stream of water, and a side stream of hydrocarbons boiling abovethe gas oil range. The overhead vapor stream from the sand trap andliquidvapor separator is reduced substantially in pressure and cooledand thereafter passed to a low temperature and low pressure zone torecover an overhead vapor stream of H2O, N2, CO, and CO2, a bottomsWater stream, and a side stream of hydrocarbons ranging from gas oil tonormally gaseous hydrocarbons. The liquid side stream is fractionated torecover a normally gaseous hydrocarbon stream, a gasoline stream, adistillate stream, and a gas -oil bottoms stream. Apparatus foreffecting the process is provided.

This invention relates to a process and apparatus for rening the hightemperature and high pressure efliuent from a production well of an insitu combustion operation.

The production of oil from subterranean oil-bearing strata by in situcombustion is an established commercial operation. The produced effluentfrom such an operation conducted by direct drive of the combustion frontis at an elevated temperature and pressure during that phase of theoperation when the combustion zone is approaching the production well.During the entire period of a reverse burning operation, the producedeluent is at a relatively high temperature and pressure due to the factthat the fire front is initiated at the production well and, as thefront moves radially outwardly therefrom, the hot combustion productsand hydrocarbons pass thru only the hot sand or rock intermediate thefire front and the production well.

The hot eiuent from an in situ combustion process contains substantialconcentrations of H2O, N2, CO, and CO2 in addition to hydrocarbonsranging from normally gaseous to heavy residual hydrocarbons. Toillustrate, when producing in-place oil of about 8 to 10 API gravity byreverse burning, the oil is upgraded underground to about 26-27 API at60 F.

The hot effluent from the production well in an in situ combustionoperation contains such high concentrations of water and nitrogen thatrefining of the effluent near the wellhead or in the field beingproduced has numerous advantages over transporting the etliuent thrupipeline or other means to a distant refinery for processing.

This invention is concerned with an arrangement of apparatus and processfor the refining of the hot high pressure eiuent from an in situcombustion processV near the wellhead,

Fice

Accordingly, it is an object of the invention to provide an improvedprocess and arrangement of apparatus for refining the high temperature,high pressure effluent from an in situ combustion process effected in asubterranean deposit of oil. Another object is to provide a process andapparatus which removes water, nitrogen, and other nonhydrocarbonmaterials from an in situ combustion eflluent. A further object is toreduce the cost and time required for recovering hydrocarbons from an insitu combustion operation and to transport the hydrocarbon phase of suchan operation to market. Other objects of the invention will becomeapparent to one skilled in the art upon consideration of theaccompanying disclosure.

1n accordance with the invention the hot vapor-liquid mixture from aproduction well in an in situ combustion operation is charged to a sandtrap and liquid-vaporseparator to remove sand and other solids from thestream and to recover a separate vapor stream comprising N2, H2O, andhydrocarbons boiling in the gas oil range and lower at relatively highpressure and temperature and a separate liquid stream comprising waterand hydrocarbons boiling above the gas oil range. The liquid streamcomprising water and high boiling hydrocarbons is ashed in a flashingzone or liash vessel to separate an overhead vapor stream and a bottomsliquid stream comprising principally high boiling hydrocarbons andwater. This liquid stream in the form of an emulsion is then passed toan emulsion breaker to effect separation of same into an overhead vaporstream, a bottom water stream, and a side stream of residualhydrocarbons boiling above the gas oil range. The overhead vapor streamfrom the sand trap and liquid-vapor separator, containing principallyH2O, N2, CO2, CO, and hydrocarbons ranging from gas oil to normallygaseous hydrocarbons, is substantially reduced in pressure and cooledbefore passing into a low temperature and low pressure separator toseparate same into an overhead vapor stream comprising principally H2O,N2, CO, and CO2, a bottom water stream, and a side stream comprisingprincipally hydrocarbons ranging from gas oil to normally gaseoushydrocarbons. This liquid side stream is fractionated in a conventionaldistillation column or fractionator to recover an overhead normallygaseous hydrocarbon stream, a stream of gasoline, a distillate sidestream, and a bottoms gas oil stream.

In instances where the residual oil from the emulsion breaker is of highenough quality, a portion of this stream -is admixed with the liquidhydrocarbon stream passing into the fractionator to recover valuablelighter constituents therefrom, the heavier portions of this residualoil being recovered in the gas oil.

A more complete understanding of the invention may be had by referenceto the drawing which is a process ow illustrating a preferredarrangement of apparatus in accordance with the invention.

Referring to the drawing, a production line 10 connects with thewellhead of a production well 12 of an in situ combustion eld operation.Line 10 leads into sand trap Vand liquid-vapor separator 14. Pressure inline 10 can be controlled within limits by means of vent line 16containing a motor valve 18 under the control of a pressure controller20 which is sensitive to pressure in line 10 Idownstre-am of line 16.Vessel 14 is an upright elongated vessel having overhead vapor line 22,a bottom outlet line 24 for sand, and line 26 for withdrawing a liquidside stream comprising principally water and hydrocarbons. Line 26 leadsin dash vessel 2S and is provided with a motor valve 30 which isoperated by liquid level controller 32 to maintain a suitable liquidlevel in vessel 14.

Vessel 28 has an overhead vapor line 34 and a bottom liquid line 36which leads into an emulsion breaker 38 comprising 'an upright elongatedvessel which is provided With a pair of liquid level .controllers 40:and 42 for maintaining suitable levels of residual hydrocarbon andWater, respectively. An overhead vapor line 44 connects with line 34 andVents thru line 46 under pressure controller 48 which operates motorvalve 50. Level controller 42, which is sensitive to the interface levelof the water and oil, operates motor valve l52 in eiuent water line 4t-o maintain a suitable water level in the lower section of vessel 38.Level controller 40 manipulates a motor valve 56 in euent residual oilline 58 -to maintain a suitable selected hydrocarbon level .in vessel38. Line 58 conducts recovered residual oil to storage or furtherrefining, as desired.

Overhead vapor line 22 leads into line 60 which contains a pressurecontroller V62 operatively connected with a motor valve 64 for reducingpressure in said line to a predetermined level. Line 60 also contains acondenser or heat exchanger 66. Separator 68 is positioned at thedownstream end of line 60 =to receive overhead feed from vessel 14,which contains a wide distribution of hydrocarbons in accordance withtheir boiling range from gas oil to normally gaseous hydrocarbons.Vessel 68 is provided with an overhead vapor line 70 in which ispositioned a motor valve 72 which is operated by a pressure controller74 to maintain `suitable backpressure on vessel 68. Water line 76 leadsfrom the bottom of vessel I68 and liquid hydrocarbon line 78 conducts aside stream of liquid hydrocarbon into fractionator v80 as feed thereto.A suitable liquid level of Water is maintained in the lower section ofvessel 68 by means of interface level controller 82 which is in controlof m0- tor valve 84 in line '76. In la similar manner Iasuitablehydrocarbon level is maintained lin vessel 68 by means of levelcontroller 86 which is in operative control of motor v-alve 88 in line78.

fEractioniator 80, which is a conventional fractional distillationcolumn, is provided with an overhead vapor line 90 containing lacondenser 92 and leading into an accumulator 94. Line 96, leading fromthe bottom of accumulator 94, is provided with a pump 98 which forcesgasoline as re'ux back to ythe upper section of -fractionator 80 thruline 100 and also passes gasoline thru line 102 to storage under thecontrol of -level controller 104 which operatively controls valve l106in line 102. Line r108 vents normally gaseous materials from accumulator94 under the control of pressure controller [L10 and motor valve 112.

Distillate line 1'14 leads into accumulator 116 which is provided withan overhead vapor line 118 and a liquid outlet line 120 containing pump122. Reliux line :124 leads from line 120 into column '80 and isprovided with `a motor valve 126 which is operated by level controller128 on accumulator 116. Distillate recovery line 130 leads to storageand is provided with a suitable backpressure valve 1132, when necessary,or pumping into a storage tank provides Athe necessary b-ackpressure.

A reboiler 134 in reboil line 136 provides reboil heat for column 80.Gas oil product line 138 connects with reboil line 136 intermediatereboiler 134 and a pump 140 therein and passes thru a heat exchanger-142 in line 78 to recover heat from the gas oil and preheat the feed inline 78. A by-pass line 144 around heat exchanger 1,42 provides forby-passing all or any desired proportion of the gas oil `around theexchanger.

Line 146 connects oil residue line 58 with line 78 .-to permit passingany desired amount of the residual oil into the hydrocarbon feed in line78 passing into fractionator I80. Auxiliary line 148 connects line 10with line 60 to provide for by-passing vapor from line 10 Ito line 60yaround vessel 14 when desired.

In order to further illustrate the invention .the following example ispresented. The data ytherein are not to be construed as unnecessarilylimiting the invention.

' EXAMPLE Specific Ranges Well Fluid (line 10):

Quantity, #/hr 33, 874 Vapor, wt. Percent. 31. 8 Liquid, Wt. Percent.68. 2 Oil, API at 60 F 26 Temperature, F Pressure, p.s.1.a Sand Trap andLiquid-Vapor Separator (14):

Temperature, F Pressure, p.s.i.a

ge, #/hL.

Temperature, F Pressure, p.s.1.a. Charge, #/hr Vapor-Steam Yield, #/hrResidue Oil, Yield, #/hr- API at 60 F Low Temperature-Low Pressure WaterSeparator (68):

Temperature, F Pressure, p.s.i.a Charge, #Ihr Vapor, wt. Percent..-Liquid, wt. Percent. Water Liquid Yield, #/hr Vapor Yield, #/hr LiquidYield, #Ihr Fractionator (BO):

Temperature, Top, F

The above .data under the Specilic column illustrate preferred operationwhen 1relining the production Well euent from a reverse in situcombustion operation in an oil Ideposit in which the oil has an APIgravity of about 8 to l0. This type has been upgraded by in situcombustion to 26-27 API gravity. Obviously, the inve -I tion isapplicable to the refining of production Well effluent fromsubstantially any in situ combustion operation which upgrades Ithe oilto the range of 20-35 API gravity. Usually the AZPI gravity of theirl-place oil will be in the range of about 8-20.

Certain modilications of the invention will become apparent to thoseskilled in the art and the illustrative details disclosed are not to beconstrued as imposing unnecessary limitations on the invention.

I claim:

1. A process for refining an eiflulent stream from a production Well ofan in situ combustion operation wherein said stream is at a temperatureof at least 300 F. and a pressure of at least 500 p.s.i.a, whichcomprises the steps of:

(a) passing said stream into a solids-liquid-vapor separating zone andseparately recovering therein entrained solids, a vapor stream at atemperature in the range of 300 to 650 F. and a pressure in the range of500 to 2000 p.s.i.a., and an unvaporized liquid stream at saidtemperature and pressure;

` (b) ashing the unvaporized liquid stream recovered in step (a) in aflashing zone at a temperature in the range of 230 to 350 F. and apressure in the range of 25 to 150 p.s.i.a. to recover an overhead vaporstream and a liquid bottoms stream in the form of a liquid-vaporemulsion;

(c) separaitng the bottoms stream of step (b) in an emulsion breakingzone at substantially the same temperature and pressure as in step (b)into an overhead vapor stream, a bottom water stream, and a residualhydrocarbon side stream;

(d) passing the vapor stream of step (a) into a lowtemperatureseparation zone operated at a temperature in the range of to 150 F. anda pressure in the range of 50 to 150 p.s.i.a to separate same into anoverhead vapor stream comprising principally steam, and a side stream ofhydrocarbons ranging from normally gaseous thru gas oil; and

(e) fractionating the side stream of hydrocarbons of step (c) to recoverseparate streams of normally gaseous hydrocarbons, gasoline boilingrange hydrocarbons, distillate, and gas oil.

2. The process of claim 1 wherein the stream of step (a) is from areverse burning combustion front in an oil stratum containing a low APIgravity oil and the oil in said stream has an API vgravity in the rangeof 20 to 35.

References Cited UNITED STATES PATENTS Shipley et al 208-187 Marx et al.196-98 Walker et al 20S-'187 Woertz 260-676 Lenhart 20S-'187 X

